Chinese Long March 4C launches Yaogan-19 Remote-Sensing Spacecraft

November 20, 2013

Photo: Xinhua

A Chinese Long March 4C Launch Vehicle blasted off from LC-9 at the Taiyuan Satellite Launch Center on Wednesday carrying the Yaogan-19 remote-sensing satellite to orbit. Liftoff from the launch base located in the Shanxi Province took place at 3:31 UTC. Official confirmation of mission success was given later on Wednesday.

This is a back-to-back launch for China as the most recent Chinese launch also took off from Taiyuan LC-9 – featuring a Long March 2C that was carrying the Yaogan 18 payload. The frequency of Yaogan launches to maintain and expand the satellite constellation shows its importance within China’s space program.

According to Chinese Officials, the Yaogan Satellite Constellation is used for scientific experiments, land survey, crop yield assessment, and disaster monitoring. However, it is believed that the satellite system serves military purposes.

The real purpose of the satellites is likely optical surveillance and tracking warships by acquiring their optical signatures and radio transmissions.

Yaogan Satellites either carry an optical imaging payload, a Synthetic Aperture Radar payload or an Electronic Intelligence package. Satellites carrying an optical imager were developed by the Shanghai Academy of Space Flight Technology while the SAR spacecraft were developed by the China Academy of Space Technology.

The first Yaogan satellite was launched on April 27, 2006 by a Long March 4B blasting off from Taiyuan. The Yaogan-1 satellite was found in a 636-Kilometer orbit at an inclination of 97.9 degrees, but details on the satellite were a closely guarded secret. Later, it became known that the spacecraft was equipped with the first space-based Synthetic Aperture Radar payload.

Yaogan-2 was launched on May 2007 by a CZ-2D lifting off from Jiquan. It settled in a similar orbit, slightly higher than Yaogan-1, but also with a 97.9-degree inclination. Details on the spacecraft were once again restricted, but it was claimed that this satellite was carrying an electro-optical imaging payload to complement the data acquired by Yaogan-1.

Also in 2007, Yaogan-3 was launched. It featured a design identical to that of Yaogan-1 and was delivered to an identical orbit, using a Long March 4C launching from Taiyuan. In 2008, two optical satellites were launched – one from Jiquan atop a Long March 2D and one aboard a CZ-4B from Taiyuan. The second of those two satellites settled in a lower orbit and is suspected to be a second generation electro-optical satellite.

2009 featured three Yaogan launches including the first second-generation SAR satellite known as Yaogan-6 that was launched in April by a Long March 2C. Two optical satellites were launched in December 2009: Yaogan-7 – a first generation optical satellite and Yaogan–8 that carried a new type of optical payload. Yaogan-8 was delivered to an orbit at an altitude of more than 1,000 Kilometers at an inclination of 100.5 degrees.

After the Yaogan-9 payload had arrived in orbit, analysts were in for a surprise as three spacecraft were detected flying in a highly choreographed, triangular constellation in a 1,080 by 1,100-Kilometer Orbit at an inclination of 63.4 degrees - resembling the US NOSS triplets that were used for ELINT purposes until being replaced by duos of NOSS (Naval Ocean Surveillance System) starting to be launched in 2001.

Yaogan-10, a first-generation SAR satellite, was launched in August 2010, followed by Yaogan-11 in September which was a first generation optical spacecraft. In 2011, another two Yaogan satellites were delivered to orbit – one equipped with a 2nd generation optical and the other with a 2nd generation SAR payload.

Three Yaogan launches took place last year as a Long March 4B delivered Yaogan-14 to orbit carrying an optical payload. Yaogan-15 was launched atop a Long March 4C and featured an optical reconnaissance payload similar to Yaogan-8 (based on launch vehicle configuration & insertion orbit). The third launch of 2012 delivered another Yaogan triplet to orbit and the first Yaogan launch in 2013, Yaogan-17, also orbited a trio of spacecraft. Yaogan-18 was launched in October 2013.

Wednesday’s launch was China’s 185th successful orbital launch, the 184th flight of the Long March series and the 11th successful Chinese orbital launch in 2013.

Yaogan-19 is likely a Yaogan-8/15-class optical reconnaissance spacecraft based on the launch vehicle configuration and launch site. Orbital parameters, once issued, will confirm the identity of the Yaogan-19 satellite.

The Long march 4C Launch Vehicle is part of China's flight proven Long March Rocket family. It is derived from the CZ-4B Launcher, but features a re-startable upper stage and can accommodate a larger Payload Fairing. It is operated from the Jiquan and Taiyuan Satellite Launch Centers. CZ-4C has a liftoff mass of 250,000 Kilograms and is 45.8 meters in length with a diameter of 3.35 meters. It features several improvements over the CZ-4B such as new telemetry, tracking, control, and self-destruction systems that are smaller in size. The first stage of the vehicle is powered by a YF-21B Rocket Engine which consists of a cluster of four YF-20B Engines each providing 814 Kilonewtons of Vacuum Thrust. At liftoff, the YF-21B provides a thrust of 2,962 Kilonewtons generating a total Thrust-to-Weight ratio of 1.21. The Engine Assembly has a weight of 2,850 Kilograms, is 3.3 meters in length and 3.5 meters in diameter. The engine nozzles are gimbaled for vehicle control. All three Stages of the vehicle use Nitrogen Tetroxide as oxidizer and Unsymmetrical Dimethylhydrazine as fuel. The first stage has a liftoff mass of 193,300 Kilograms including 183,300 Kilograms of propellants. It is 24.7 meters in length. The second stage of the vehicle is powered by a YF-22B Main Engine providing 738 Kilonewtons of thrust and a four-chamber vernier yet designated YF-23F providing 46 Kilonewtons of thrust. The main engines is fixed while the four vernier nozzles can be gimbaled for attitude control during powered flight. The stage is 10.4 meters long and holds 35,370 Kilograms of storable propellants. Both, the first and second stage, are based on components that are flown on other CZ Rockets. The third stage however, is a specially designed rocket stage for the Long March 4C and its purposes. The stage is 4.9 meters long and has a reduced diameter of 2.9 meters. Liftoff mass is 14,560 Kilograms including 12,800 Kilograms of propellants.

Photo: Xinhua

Photo: Xinhua

It uses a 98-Kilonewton YF-40 Rocket Engine. YF-40 has a dry weight of approximately 166 Kilograms and a diameter of 0.65 meters. It provides re-ignition capability to the vehicle in order to target a variety of orbits and provide precise injection capabilities. Long March 4C is capable of delivering payloads of up to 4,200 Kilograms to Low Earth Orbit. Sun Synchronous Orbit capability is 2,800 Kilograms and Payloads of up to 1,500 Kilograms can be delivered to Geostationary Transfer Orbit by the Long March 4C.

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